Regional Climate Model Simulation of Summer Rainfall over Southeast China

It is widely known that the simulation of regional rainfall is sensitive to the selection of cumulus convection scheme and is very locally dependent. Although numerous studies have examined the models' ability in capturing the characteristics of rainfall over various areas, studies have rarely focused on the simulation of rainfall over Southeast China (P_SEC). In particular, a suitable model simulation for the sub-daily variation of P_SEC has not been identified. This issue, which is important to the regional community, is addressed in this study by examining the capability of third-generation Regional Climate Model (RegCM3) in simulating the P_SEC during the 1998-2002 summer seasons. The RegCM3 has four available choices of cumulus schemes: EMU, GFC, GAS and AK. Our analyses indicate that EMU is better than other schemes in simulating the summer mean P_SEC, while GFC has the best simulation ability to the sub-daily variations of P_SEC. Examination on the water vapor budget further points out that the convective scheme configuration which has more correct simulation of moisture flux convergence can simulate a more realistic evolution of P_SEC. In addition to cumulus convection schemes, it is also found that the modification of domain orientation also has large impact on the simulation of rainfall as well as atmospheric circulation. Results suggest that in order to obtain a proper simulation of rainfall over East Asia, the use of a model domain covering whole Tibetan Plateau is necessary and important.